In furnaces used throughout the metallurgical and related industries to heat a slab, billet, bloom or other raw steel shape, a typical furnace includes a complex network of vertical and horizontal water-cooled pipes which support an additional network of horizontal water-cooled skid rails along which the slabs, billets, blooms, or other raw steel shapes are pushed or walked through the furnace. The metallurgical furnace is an open system; that is, heat which is transferred to the metal pipe network is conducted by the flowing water in the pipes to a point outside the furnace and is not recoverable. Accordingly, vast amounts of heat losses occur and correspondingly unnecessary amounts of energy are expended to replace the heat loss as a result of the heat transfer into the water-cooled pipe network. For example, as much as thirty to thirty-five percent of the total heat supplied to a metallurgical furnace by the combustion of fuels is lost in an infrastructure of uninsulated skid pipes and the supporting pipe network. For a 41/2 inch OD uninsulated water-cooled pipe in a furnace operating at 2400.degree.-2500.degree. F., the heat loss is approximately 115,000-120,000 Btu per lineal foot per hour. For a furnace having 200 feet of skid pipe, 200 feet of horizontal support and 200 feet of vertical support pipe, the heat loss is thus approximately 600.times.117,500 Btu/hour or 70,500,000 Btu per hour. Hence, the more effective the insulator or refractory around the pipe network, the more efficient and the more economical is the furnace to operate..
To date, various types of refractory materials have been utilized in order to reduce the amount of heat loss from the furnace through the water-cooled pipe infrastructure. The use of pre-fired or chemically bonded refractory materials which are welded, studded, wired, clipped or anchored with interlocking anchor straps is well known. The use of welds, studs, wires and the like requires large expenditures of labor and time to strip the pipe and secure an additional refractory as a replacement. Moreover, refractory concretes have even been formed in place around the pipe surfaces which are supported by any number and type of metallic anchors welded to the pipe surface. Almost without exception these forms of insulation have failed within a relatively short period of operation because of the inherent friability and susceptibility to fracture of the heavy, brittle fired ceramic refractory materials. As the metallic shape is moved along the metal skid rail, significant vibration and flexion of the water-cooled pipe infrastructure occur which are in turn transmitted into the friable, dense, rigid ceramic insulators. High temperature ceramic fiber blankets in the form of split rings, modules or simple wrappings have also been utilized as a means of insulating the pipe infrastructure. The use of ordinary high temperature ceramic fibers and ceramic fiber blankets as insulators around the water-cooled pipe has proven unsatisfactory for a number of reasons: first, the ordinary high temperature ceramic fiber blanket is susceptible to chemical reaction with scale and slag which is produced during the furnace operation; second, ordinary ceramic fiber blankets are inherently susceptible to erosion by the velocities of the gases within the furnace; and third, the ceramic fiber blankets have been difficult to attach to the pipe and suffer a notable shrinkage due to the high temperatures of the furnace.
Covering the ceramic fiber blanket with a rigid preburned ceramic tile refractory has proven less than desirable. Fractures in the refractory and the failure to form an intimate fit among the refractory segments has in effect exposed the ceramic fiber blanket underneath to the deleterious effects of the furnace noted above. Furthermore, the high specific weight of the preburned ceramic tile refractory has compressed the blanket underneath and has further chafed holes in the blanket from the movement of the tile on the blanket as the pipe is vibrated and flexed during furnace operations.